>>58750146I don't know why gamefreak feels the need to include all regional forms of a given mon, anyway. We've had dex cuts AND form cuts before. Why not limit the next gen to only having alolan meowth instead of randomly including the other two? etc. It was... cute, I guess, in sm, when visitors from kanto had their original forms. But that's not required for the concept at all.
It's just more 'tism. Beyond that they could easily pivot to using them for biome-dependency; alolan vulpix in a snow biome outside of alola: "These vulpix are remarkably similar to the forma native to the Alola region." as a dex entry. Done. Easy.